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Nutrient Network Collaborative Research

co-PIs Sarah Hobbie and Melanie Mayes

The overarching goal of this research is to use a continental-scale network of replicated, long-term grassland nutrient addition experiments, the Nutrient Network, to enhance the Microbial ENzyme Decomposition (MEND) model towards determining how N inputs affect: (1) biochemical stabilization of soil organic matter (SOM) by altering the quantity and quality of plant inputs to soils, and soil microbial community structure, stoichiometry, and functional potential; and (2) physicochemical stabilization of SOM by altering soil aggregate formation and SOM-mineral interactions. At ten Central Great Plains Nutrient Network experiments that span soil texture and water balance gradients, the project will examine N enrichment effects on SOM dynamics, and the mechanisms underpinning such effects, by measuring the stoichiometry and quantities of plant inputs; the stoichiometry, composition, and activity of soil microbes; and the formation of micro- and macroaggregates. Empirical work on C-N interactions will be integrated into a modeling framework, via parameterization, model development, and model evaluation of the MEND model. MEND will be used to explore the combined effects of N enrichment on SOM dynamics via altered litter inputs and stoichiometry, microbial communities, microbial biomass, and hydrolytic vs. oxidative enzyme activity, to determine whether the proposed model structure captures the variation in soil C responses to N additions observed across the Central Great Plains.

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